Machine cables are typically used to provide an electrical connection for mobile electrical machines. For example, in the mining or petroleum industry often large electrical machinery is used and each machine cable may have to provide power in the order of a few hundred kilowatts to a few megawatts. Typically such power is delivered with a voltage of one or more kilovolts. The cables usually comprise a plurality of cores and are connected using electrical connection devices including sockets, pins and thimbles.
The cores typically are insulated from each other and surrounded by a conductive layer that is on earth potential. Therefore, if the cores break, individual broken cores are less likely to be in electrical contact with each other, but instead are likely to be in electrical contact with respective layers that are on earth potential. Often automatic electrical earth leakage protection devices are used and in case of electrical contact between one of the cores and one or more layers that are on earth potential, an automatic electrical earth leakage protection device will detect an earth leakage current in the order of 30 mA and subsequently interrupt the supply of electricity. Therefore, melt-down of the cable, electrical arcing and the like can largely be avoided. However, within a plug/coupling connection (electrical device) individual cores typically are not surrounded by individual layers on earth potential but are stripped off the layer and are surrounded by a common electrical casing that is on earth potential. Therefore, if individual cores are disrupted within the plug, it is more likely that the disrupted cores are in direct electrical contact with each other with fault current capacities of 10 kA to 50 kA. This will have dangerous consequences especially in an environment that may contain explosive gases such as a mine.